My car's dashboard lighting uses six B9 base incandescent bulbs . The brightness of these bulbs is controlled through a wire-wound variable-resistance potentiometer with an output of 0-12VDC. This is an antique vehicle with basic, non-modern, non-electronic wiring.
I want to replace the incandescent bulbs with LED bulbs also having B9 bases without having to add an additional control, just using the present controller.
Is there a device I can add to the potentiometer output that will convert the variable (0-12VDC) voltage to PWM to drive the bulbs? It would go in the green wire in this diagram:
Best Answer
I assume you are looking for something off the shelf and not looking to construct a circuit from scratch.
Fan speed controllers are commercially available that can drive 12v led bulbs instead of fans. I would recommend using something like this:
https://www.amazon.com/Pixnor-Controller-Adjustable-Reversible-reversing/dp/B01H1W79S0/ref=pd_sim_60_7?_encoding=UTF8&psc=1&refRID=JX2HZEZDTSYRJ3TG651Q
And replacing the existing potentiometer with the one mounted on the board. It would also be possible to use the existing potentiometer (assuming it is a 3 terminal potentiometer not a 2 terminal rheostat) by either disconnecting it from all current wiring and wiring it to the board, or using a resistive divider to change the output voltage range of on the orange wire to what the board expects. If you want to go this way, post a follow up and I will post instructions on how to figure out what resistors to use.
Note that you don't want to use a fan speed controller rated for 12 or 15v because the voltages on car electrical systems can exceed the nominal 13.5V the alternator/generator outputs significantly when the engine is turned off.